Flat Wart

Flat warts (verruca plana) are smooth, flat topped papules caused by human papillomavirus types 3, 10, 28 and 49. They are common in children and young adults, affecting the face, dorsa of hands and shins.

• Spread by autoinoculation along skin trauma (Koebner), shaving and scratching.
• Extensive, early onset or persistent disease may indicate epidermodysplasia verruciformis or immunosuppression.

Multiple 1 to 5 mm flat to slightly raised papules, skin coloured, pink or light brown, often in linear streaks.

• Face (forehead, cheeks, chin), dorsum of hands, forearms, legs, beard area in men and shaved legs in women.
• Asymptomatic or mildly itchy; cosmetic distress.
• Differential diagnosis: lichen planus, seborrhoeic keratosis, syringoma, acrokeratosis verruciformis, epidermodysplasia verruciformis, molluscum contagiosum, lichen nitidus, actinic keratosis, plane xanthoma, early squamous cell carcinoma.
• Complications: post inflammatory hyperpigmentation, scarring from aggressive treatment, recurrence, widespread disease, malignant change in epidermodysplasia verruciformis.

Clinical; dermoscopy shows regularly distributed red or brown dots.

• Biopsy if atypical, resistant or in the immunosuppressed.
• HIV test and review of medicines in extensive disease; genetic evaluation if early onset extensive and persistent lesions.

Gentle, field directed treatment to avoid scarring and pigment change.

• Supportive: stop shaving over lesions or use an electric razor, sun protection, avoid picking and scratching, sunscreen SPF 30 or more.
• Pharmacological: tretinoin 0.025 to 0.05 percent cream nightly; imiquimod 5 percent cream three times weekly; fluorouracil 5 percent cream twice daily for 3 to 4 weeks (apply carefully to face and expect irritation); salicylic acid 2 to 5 percent lotion daily; glycolic acid 10 to 15 percent peels. Oral isotretinoin 0.5 mg/kg daily for resistant extensive disease under specialist care. Intralesional Candida antigen or MMR vaccine for multiple lesions.
• Procedures: very light cryotherapy (3 to 5 seconds), trichloroacetic acid 35 percent touch peel, curettage or light electrodessication, pulsed dye laser. Avoid deep destruction on the face.
• Special groups: pregnancy, avoid tretinoin, isotretinoin, imiquimod and fluorouracil; use salicylic acid sparingly or defer treatment; children, topical keratolytics and watchful waiting; darker skin types, high risk of hyperpigmentation, so avoid aggressive treatments; HIV, treat HIV and apply topical therapies.
• Red flags: rapid spread, immunosuppression, pigmented or ulcerated lesions, scarring, atypical morphology.
• Follow-up: review every 4 weeks; reassess diagnosis at 12 weeks; biopsy resistant lesions.